<!DOCTYPE html>
<html>
<head>
  <meta charset="UTF-8">
  <title>计科2412 04 洪语梵</title>
  <style>
    div {
      margin: 8px 0;
      padding: 6px;
      width: 200px;
    }
    .d1 {
      border: 1px solid #999;
      background-color: #f5f5f5;
    }
    .d1.d2 {
      background-color: #e3f2fd;
      border-color: #2196f3;
      box-shadow: 0 2px 4px rgba(0,0,0,0.1);
    }
    #d3 {
      color: #d32f2f;
      font-size: 18px;
      font-weight: bold;
      border: 1px solid #d32f2f;
    }
    div[ab="d4"] {
      color: #388e3c;
      font-style: italic;
      border: 1px dashed #388e3c;
      background-color: #e8f5e9;
    }
  </style>
</head>
<body>
  <div>1</div>
  <div class="d1">1</div>
  <div class="d1 d2">2</div>
  <div id="d3">3</div>
  <div ab="d4">4</div>
</body>
</html>